The invention relates to a triple pole semiconductor arrangement for switching large currents having two transistors of the same region sequence which are connected together like a Darlington circuit, one of these transistors acting as a driving transistor for the output transistor which switches the current.
In the Darlington circuit, the collectors of the two transistors are connected together while the emitter electrode of the driving transistor is connected to the base electrode of the output transistor. The compound circuit may be regarded as a single transistor whose amplification of current is approximately equal to the product of the current amplifications of the two individual transistors. This depends on the fact that the emitter current of the driving transistor is equal to the base current of the output power transistor. The Darlington circuit has the advantage that even large currents may be switched by small control currents so that the control currents required may be taken directly from a integrated switching circuit. In the Darlington circuit it is disadvantageous that the switching times are relatively long. Even when offering a large reverse current in the disconnection phase, with the Darlington transistor the switching time cannot be substantially reduced.
Furthermore the Darlington circuit has the disadvantage that at high temperatures it no longer operates as a switch in many cases. This is caused by the fact that at high temperatures the base current of the final transistor becomes so large that this output transistor constantly remains switched on.